Reduction of Audio Noise with Lowpass Chebyshev Type II Filter Simulated using GNU Octave

Audio signal is one of the most used signals especially in the development of communication technology. One common audio signal is a human voice recording. In such signal, there is a segment called unvoiced recording. These segments were usually noise produced in the background or in the device used. This research proposes to simulate the removal of equipment and environmental noise in an audio using Digital Lowpass Chebyshev type II filter. Audio signal samples were gathered using a voice recorder device. The saved file will be filter using GNU Octave software. Then, the processed sound signals are amplified for higher power. The filter designed lowpass filter was expected to attenuate the passband in the frequency of 200 Hz with 10 dB and the stopband in the frequency of 250 Hz, 275 Hz, and 300 Hz with 40 dB. Among the three different specifications of the filter, the filter that has a stopband frequency of 300 Hz exhibits the lowest value of mean and median error.